With increasing development of electronic industries, the internal circuitries of an electronic device are advanced toward modularization and miniaturization. For example, plural electronic components are mounted on a printed circuit board and thus many functions are integrated into a single circuit module. For example, a power module is a common circuit module. Via an edge connector, the power module is vertically mounted on a system circuit board so as to allow for high-density mounting and increase space utilization of the system circuit board. During the wave soldering process, the power module may be rocked or tilted such that the electronic components on the power module possibly collide with the electronic components on the system circuit board. In this circumstance, the electronic device is possibly short-circuited or even damaged. Therefore, several support structures have been proposed for assisting the power module to be firmly fixed on the system circuit board.
Please refer to FIG. 1, which is a schematic perspective view illustrating a circuit module mounted on a system circuit board. The circuit module is a power module or other functional module. As shown in FIG. 1, the circuit module 10 includes a printed circuit board 11, plural electronic component 12, plural pins 13 and a heat sink 14. The printed circuit board 11 is vertically mounted on a system circuit board 20 so as to allow for high-density mounting and increase space utilization of the system circuit board 20. The pins 13 are protruded from a lower edge of the printed circuit board 11. The pins 13 are inserted into corresponding through-holes 21 in the system circuit board 20 and then welded onto the system circuit board 20 in order to fix the circuit module 10 and permit electrical connection between the printed circuit board 11 and the system circuit board 20.
For assisting the circuit module 10 to be firmly fixed on the system circuit board 20, two of more support pins 13′ are inserted into corresponding retaining holes 22 in the system circuit board 20 and then welded onto the system circuit board 20. In addition, since the diameter of the retaining hole 22 is smaller than that of the through-hole 21, the support pins 13′ may be tight-fitted into the retaining holes 22 to further facilitate supporting the circuit module 10. The support structure may reduce the possibility of rocking or tilting the circuit module 10 during the wave soldering process. In addition, by means of the support structure, the circuit module 10 will not be uplifted due to the buoyancy of the flux composition and thus the edge side of the circuit module 10 may lie flat on the system circuit board 20. Under this circumstance, the possibility of causing short-circuited or damaged electronic device is reduced. This support structure, however, still has some drawbacks. For example, the support pins 13′ fail to be fixed onto the system circuit board 20 due to the poor wetting property and the poor solderability because the diameter of the retaining hole 22 is relatively smaller than that of a standard soldering hole. Since the flux composition is difficulty permeated through the retaining hole 22 to the corresponding contact pad (not shown) on the system circuit board 20, the adhesion between the support pin 13′ and the system circuit board 20 is not sufficient. If the height of the circuit module 10 is very high, the circuit module 10 is still tilted.
As shown in FIG. 2, a jig member 30 is used to suppress the circuit module 10 in order to further assist fixing the circuit module 10 on the system circuit board 20 and avoid rocking, tilting or uplifting the circuit module 10. Generally, the jig member 30 comprises a substrate 31 and plural protrusion plates 32. The protrusion plates 32 are perpendicular to the substrate 31. A receiving portion is defined between two adjacent protrusion plates 32. The width of the receiving portion is substantially equal to the width of the circuit module 10 and the upper edge of the circuit module 10 is received in the receiving portion. Since the heights of the electronic components on the circuit module 10 are usually unequal and some electronic components on the system circuit board 20 are arranged beside the circuit module 10, it is difficult to properly place the jig member 30 on the circuit module 10. Moreover, during the process of placing the jig member 30 on the circuit module 10, the electronic components on the circuit module 10 or the system circuit board 20 are readily collided with the circuit module 10 and thus damaged.
In order to further assist fixing the circuit module 10 on the system circuit board 20 and avoid rocking, tilting or uplifting the circuit module 10, a tape 40 is used to confine the circuit module 10 in position. Usually, both ends of the tape 40 are bonded to corresponding electronic components 23 on the system circuit board 20. Since the tape 40 offers poor adhesion, the power module 10 may still be rocked or tilted.
In views of the above-described disadvantages resulted from the prior art, the applicant keeps on carving unflaggingly to develop an improved support structure of a circuit module according to the present invention through wholehearted experience and research.